POSITIONAL CHANGE MEASUREMENT DEVICE, POSITIONAL CHANGE MEASUREMENT METHOD, AND IMAGE FORMING APPARATUS

• US 20140268180A1
• Filed: 03/13/2014
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Atsushi Takaura, Kenichi Shimizu, Koichi Kudo, Koji Masuda, Takeshi Ueda, Taku Amada, Yasuhiro Nihei
• Inventors: MASUDA, Koji, NIHEI, Yasuhiro, KUDO, Koichi, TAKAURA, Atsushi, UEDA, Takeshi, AMADA, Taku, SHIMIZU, Kenichi, TAMURA, Asato
• Granted Patent: US 9,228,825 B2
• Time in Patent Office: Days
• US Class Current: 356/624
• CPC Class Codes: G01B 11/043 for measuring length
• CPC Class Codes: G03G 15/00 Apparatus for electrographic processes using a charge pattern G03G16/00, G03G17/00 take precedence ; xerographic printers for data processors per se G06K15/14
• CPC Class Codes: G03G 15/5054 by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt
• CPC Class Codes: G03G 2215/00616 Optical detector

Abstract

An objective is to achieve a positional change measurement device which measures positional change of a dynamic measured surface by using speckle patterns while easily reducing influence of fluctuations in a measurement environment temperature. Provided is a positional change measurement device including: a light source; an illuminating optical system configured to guide light from the light source to a measured surface; an imaging optical system; an image pickup device configured to acquire a speckle pattern by receiving reflection light from the measured surface via the imaging optical system; and detected-length compensation means for compensating for fluctuations in a detected length caused by temperature fluctuations. Positional change of the measured surface is measured based on a result of cross-correlation computation performed on multiple speckle patterns acquired at predetermined time intervals.

Claims

1. A positional change measurement device comprising:

a light source;

an illuminating optical system configured to guide light from the light source to a measured surface;

an imaging optical system;

an image pickup device configured to acquire a speckle pattern by receiving reflection light from the measured surface via the imaging optical system; and

detected-length compensation means for compensating for fluctuations in a detected length which are caused by temperature fluctuations, wherein

positional change of the measured surface is measured based on a result of cross-correlation computation performed on a plurality of speckle patterns acquired at predetermined time intervals.

2. The positional change measurement device according to claim 1, wherein

the detected-length compensation means compensates for mechanical fluctuations in the detected length due to change in positions of the light source and the illuminating optical system, by using optical fluctuations in the detected length due to change in a focal length of the imaging optical system.

3. The positional change measurement device according to claim 2, further comprising:

a support member configured to retain the light source, the illuminating optical system, the imaging optical system, and the image pickup device; and

an imaging-optical-system retaining member configured to retain the imaging optical system, wherein

the support member brings the imaging-optical-system retaining member into contact with the image pickup device and presses the imaging-optical-system retaining member in a direction along an optical axis of the imaging optical system.

4. The positional change measurement device according to claim 1, further comprising:

a lens barrel configured to retain the imaging optical system; and

a lens-barrel retaining member configured to retain the lens barrel, wherein

the lens barrel and the lens-barrel retaining member are different in their amounts of change in a direction of an optical axis of the lens barrel, the change being caused by temperature fluctuations.

5. The positional change measurement device according to claim 4, further comprising a sliding retaining member configured to enable the lens barrel to slide relative to the lens-barrel retaining member.

6. The positional change measurement device according to claim 4, further comprising an elastic member configured to bring the lens barrel into pressure contact with the image pickup device.

7. An image forming apparatus which forms an image on a surface of a mobile object traveling in a certain direction at a certain velocity, the apparatus comprising

the positional change measurement device according to claim 1, wherein

the positional change measurement device measures at least one of a traveled distance and a traveling velocity of the surface of the mobile object which is a dynamic measure surface.

8. A positional change measurement device comprising:

a light source;

an illuminating optical system configured to guide light from the light source to a measured surface;

an imaging optical system; and

an image pickup device configured to acquire a speckle pattern by receiving reflection light from the measured surface via the imaging optical system, wherein

positional change of the measured surface is measured based on a result of cross-correlation computation performed on a plurality of speckle patterns acquired at predetermined time intervals,

the imaging optical system includes, from a measured-surface side, a first group of a positive power, an aperture stop, and a second group of a positive power,

the aperture stop is provided at a position of an image-side focal plane of the first group and of an object-side focal plane of the second group,

a light-receiving surface of the image pickup device is placed at a Gaussian plane of the measured surface formed by the imaging optical system, and

the positional change measurement device satisfies;

a condition (1) D/Db=0,

where Db is a distance between a boiling plane of the measured surface and the Gaussian plane of the measured surface formed by the imaging optical system, and D is an interspace between the Gaussian plane and the light-receiving surface of the image pickup device.

9. The positional change measurement device according to claim 8, wherein

each of the first group and the second group of the imaging optical system is formed by two or more lenses made of different materials, and

irrespective of fluctuations in a measurement environment temperature, the positional change measurement device satisfies:

the condition (1) D/Db=0,

where Db is the distance between the boiling plane of the measured surface and the Gaussian plane of the measured surface formed by the imaging optical system, and D is the interspace between the Gaussian plane and the light-receiving surface of the image pickup device.

10. The positional change measurement device according to claim 8, further comprising a group-interspace adjustment mechanism configured to adjust an interspace between the first group and the second group according to an amount of fluctuations in a focal length of each of the first group and the second group constituting the imaging optical system, the fluctuations being caused by the fluctuations in the measurement environment temperature.

11. The positional change measurement device according to claim 10, wherein

the group-interspace adjustment mechanism suppresses fluctuations in an average value of magnifications of a plurality of real-image heights in a speckle pattern, the fluctuations being caused by the fluctuations in the measurement environment temperature.

12. The positional change measurement device according to claim 11, wherein

The group-interspace adjustment mechanism has a plurality of lens barrels including at least a first lens barrel configured to retain the first group and a second lens barrel configured to retain the second group, the first lens barrel and the second lens barrel having different coefficients of linear expansion,

one of the first lens barrel and the second lens barrel is fixed at one end to the image pickup device, and

elongation and contraction of the plurality of lens barrels due to the fluctuations in the measurement environment temperature are utilized to suppress the fluctuations in the average value of the magnifications of the plurality of real-image heights in the speckle pattern, the fluctuations being caused by the fluctuations in the measurement environment temperature.

13. The positional change measurement device according to claim 12, wherein

the group-interspace adjustment mechanism has the first lens barrel configured to retain the first group, a third lens barrel slidable relative to the first lens barrel, and the second lens barrel configured to retain the second group,

the first lens barrel and the third lens barrel are fixed at one ends to the image pickup device, and

elongation and contraction of any one of the first lens barrel and the third lens barrel due to the fluctuations in the measurement environment temperature are utilized to minimize the fluctuations in the average value of the magnifications of the plurality of real-image heights in the speckle pattern, the fluctuations being caused by the fluctuations in the measurement environment temperature.

14. The positional change measurement device according to claim 13, wherein

the second lens barrel and the image pickup device do not come into contact with each other irrespective of the fluctuations in the measurement environment temperature.

15. The positional change measurement device according to claim 13, wherein

an endmost surface portion of the second lens barrel located on a first-group side in a direction along an axis of the second lens barrel does not come into contact with a surface of the first lens barrel facing the endmost surface portion, irrespective of the fluctuations in the measurement environment temperature.

16. The positional change measurement device according to claim 15, further comprising a repulsive elastic member located between the first lens barrel and the second lens barrel and configured to exert an elastic force pressing the second lens barrel against the third lens barrel.

17. The positional change measurement device according to claim 16, wherein

the first lens barrel and a housing retaining the first lens barrel respectively have opposite surfaces facing each other in a direction along an axis of the first lens barrel,

the positional change measurement device comprises a compressive elastic member between the opposite surface of the first lens barrel and the opposite surface of the housing,

the repulsive elastic member exerting the elastic force pressing the second lens barrel against the third lens barrel and the compressive elastic member are both spring members,

with the repulsive elastic member expressed as a spring member A and the compressive elastic member expressed as a spring member B, the positional change measurement device satisfies conditions:

K1·

n1−

K2·

n2−

M1·

G<

0, and 

 

(3)

−

K1·

n1−

K2·

n2−

M2·

G−

M3·

G<

0, 

 

(4)

where K1 and n1 are a spring constant and a flexture amount, respectively, of the spring member A, M1 is a mass of the first lens barrel, K2 and n2 are a spring constant and a flexture amount, respectively, of the spring member B, M2 is a mass of the second lens barrel, M3 is a mass of the third lens barrel, and G is a gravitational acceleration, and

the positional change measurement device is located below the measured surface.

18. The positional change measurement device according to claim 16, wherein

the first lens barrel and a housing retaining the first lens barrel have opposite surfaces facing each other in a direction along an axis of the first lens barrel,

the positional change measurement device comprises a compressive elastic member between the opposite surface of the first lens barrel and the opposite surface of the housing,

the repulsive elastic member exerting the elastic force pressing the second lens barrel against the third lens barrel and the compressive elastic member are both spring members,

with the repulsive elastic member expressed as a spring member A and the compressive elastic member expressed as a spring member B, the positional change measurement device satisfies conditions:

−

K1·

n1+K2·

n2−

M1·

G>

0, and 

 

(5)

K1·

n1−

M3·

G>

0, 

 

(6)

where K1 and n1 are a spring constant and a flexture amount, respectively, of the spring member A, M1 is a mass of the first lens barrel, K2 and n2 are a spring constant and a flexture amount, respectively, of the spring member B, M3 is a mass of the third lens barrel, and G is a gravitational acceleration, and

the positional change measurement device is located above the measured surface.

19. An image forming apparatus which forms an image on a surface of a mobile object traveling in a certain direction, the apparatus comprising

the positional change measurement device according to claim 8, wherein

the positional change measurement device measures at least one of a traveled distance and a traveling velocity of the surface of the mobile object which is a dynamic measure surface.